Traditionally, to interact with an environment, such as a room in a home or office, users rely upon handsets or wired controls to interface devices within the environment. For example, remote controls for televisions, or light switches. In some cases a smart phone may be used to control smart devices in the home, such as light bulbs and multimedia devices. However, reliance on a handheld or accessible control may limit the freedom of users to experience their environment.
Object positioning through range finding with directional transmitters/receivers is known as SONAR (sound navigation and ranging). RADAR (radio detection and ranging) uses an ultrasonic pulse generated in a particular direction to detect objects. If an object is in the path of the pulse, part or all of the pulse will be reflected back to the transmitter as an echo and can be detected through the receiver path. By measuring the difference in time between the pulse being transmitted and the echo being received, it is possible to determine distance to an object.
Another technique used for detection of people within an environment is Infrared (IR). IR may be used to detect body heat, however IR typically requires line of site to the moving body, dedicated components, and needs relatively large surface for the lens of the sensor. Furthermore, IR devices cannot be placed near heat emitting objects like light source.
Another technique utilizes ultrasound Doppler shifts to detect movements due to reflection from the moving object. Doppler systems typically emit a single carrier, and the system measures the deviation from the single carrier. One drawback of this technique is that it requires substantial level of emitted energy, and the level of energy is bound by health regulations. Some products need to exceed allowable health regulation levels to be effective. Doppler shift techniques are also susceptible to no movement scenarios. For example, if a person is static for a period of time, the Doppler based system may determine that the room is vacant. The distance of the moving object from the detector is difficult to estimate since the indication to the position is the energy of the Doppler shift, which is dependent on many parameters apart from distance from emitter. Using pulse-reflection methods is also difficult to implement in standard rooms due to the uncontrolled reflection pattern and required pulse energy. This method also requires two transducers, one of sending and the other for receiving. Therefore, improved detection techniques for detecting and tracking positioning of objects or people within an environment is needed.